The present invention relates to a stereoimage formation apparatus for forming an erect and unmagnified stereoimage, and a stereoimage display unit for displaying an erect and unmagnified stereoimage.
Japanese Patent No. 3195249 describes a display unit that includes an erecting-unmagnifying optical system having two-dimensionally arranged microlenses. A liquid crystal display (LCD) is arranged at one side of the erecting-unmagnifying optical system. The erecting-unmagnifying optical system forms, at its side opposite to the side where the LCD is arranged, an erect and unmagnified stereoimage of an image that is displayed on the LCD. The erect and unmagnified stereoimage is clearer than a blurred background image that is displayed through a perforated color plate. When viewed with both eyes by the observer, the erect and unmagnified stereoimage is viewed as a floating image.
Japanese Laid-Open Patent Publication No. 64-88502 describes a conventional erecting-unmagnifying optical system used in a scanner or a copier. As shown in FIG. 1, the conventional erecting-unmagnifying optical system includes two lens array plates 103. Each of the lens array plates 103 has a plurality of microlenses 103a that are arranged in a manner that their optical axes are parallel to one another. The optical axes of the microlenses 103a of one lens array plate 103 are aligned with the optical axes of the microlenses 103a of the other lens array plate 103. The peaks of the microlenses 103a of one lens array plate 103 come in contact with the peaks of the microlenses 103a of the other lens array plate 103. The erecting-unmagnifying optical system whose microlenses 103a are each formed to have a small spherical aberration and produces a high-resolution image.
To produce a high-resolution image, the microlenses of conventional erecting-unmagnifying optical systems are each formed to have a small spherical aberration. In the conventional erecting-unmagnifying optical system, even a slight change in the distance between an object 15 (image on an LCD screen) and the microlenses 103a causes the image 15a to blur greatly. Thus, the positional relationship between the conventional erecting-unmagnifying optical system and the object 15 cannot be changed.
The display unit described in Japanese Patent No. 3195249 is disadvantageous in that moire may be generated. Moire is a regular stripe pattern, which is generated by interference between the microlenses and the pixels of the LCD, and is displayed together with the erect and unmagnified image. Moire lowers the image quality.
R. Rorner, “Display 20 (1999)” describes an apparatus for displaying an erect image with suppressed moire. This conventional apparatus displays an erect image on a lenticular sheet on which a plurality of cylindrical lenses are arranged. The cylindrical lenses arranged on the lenticular sheet are formed not in units of pixels but in units of sub-pixels to achieve high resolution. Each cylindrical lens emits monochromatic light of one of red, green, and blue. This structure suppresses color moire. However, it is difficult to manufacture a cylindrical lens having dimensions smaller than a pixel. In particular, it is extremely difficult to manufacture a mold for the above lenticular sheet.
Japanese Laid-Open Patent Publication No. 2004-1184140 describes an apparatus for displaying an erect image with suppressed moire. This erect image display apparatus includes a planar display and a screen. The planar display has a plurality of pixels, each of which includes three sub-pixels. The screen divides the image into disparity images by limiting the travel direction of light emitted from each sub-pixel. The disparity images are viewed by the observer as an erect image. To suppress moire, the screen includes screen elements that are arranged at intervals of total numbers of an integral multiple number of the pixel pitch and an integral multiple number of the sub-pixel pitch. With this structure, moire would be too small to be observed. However, this structure suppresses moire only when the planar display is separated by a predetermined distance from the screen. This structure does not permit the distance between the planar display and the screen to be changed.